1 # SPDX-License-Identifier: GPL-2.0-only
6 default "/lib/modules/$(shell,uname -r)/.config"
7 default "/etc/kernel-config"
8 default "/boot/config-$(shell,uname -r)"
9 default "arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)"
11 config CC_VERSION_TEXT
13 default "$(CC_VERSION_TEXT)"
15 This is used in unclear ways:
17 - Re-run Kconfig when the compiler is updated
18 The 'default' property references the environment variable,
19 CC_VERSION_TEXT so it is recorded in include/config/auto.conf.cmd.
20 When the compiler is updated, Kconfig will be invoked.
22 - Ensure full rebuild when the compiler is updated
23 include/linux/compiler-version.h contains this option in the comment
24 line so fixdep adds include/config/cc/version/text.h into the
25 auto-generated dependency. When the compiler is updated, syncconfig
26 will touch it and then every file will be rebuilt.
29 def_bool $(success,test "$(cc-name)" = GCC)
33 default $(cc-version) if CC_IS_GCC
37 def_bool $(success,test "$(cc-name)" = Clang)
41 default $(cc-version) if CC_IS_CLANG
45 def_bool $(success,test "$(ld-name)" = BFD)
49 default $(ld-version) if LD_IS_BFD
53 def_bool $(success,test "$(ld-name)" = LLD)
57 default $(ld-version) if LD_IS_LLD
62 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
63 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag))
65 config CC_CAN_LINK_STATIC
67 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
68 default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
70 config CC_HAS_ASM_GOTO
71 def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
73 config CC_HAS_ASM_GOTO_OUTPUT
74 depends on CC_HAS_ASM_GOTO
75 def_bool $(success,echo 'int foo(int x) { asm goto ("": "=r"(x) ::: bar); return x; bar: return 0; }' | $(CC) -x c - -c -o /dev/null)
77 config TOOLS_SUPPORT_RELR
78 def_bool $(success,env "CC=$(CC)" "LD=$(LD)" "NM=$(NM)" "OBJCOPY=$(OBJCOPY)" $(srctree)/scripts/tools-support-relr.sh)
80 config CC_HAS_ASM_INLINE
81 def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null)
89 config BUILDTIME_TABLE_SORT
92 config THREAD_INFO_IN_TASK
95 Select this to move thread_info off the stack into task_struct. To
96 make this work, an arch will need to remove all thread_info fields
97 except flags and fix any runtime bugs.
99 One subtle change that will be needed is to use try_get_task_stack()
100 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
109 depends on BROKEN || !SMP
112 config INIT_ENV_ARG_LIMIT
117 Maximum of each of the number of arguments and environment
118 variables passed to init from the kernel command line.
121 bool "Compile also drivers which will not load"
124 Some drivers can be compiled on a different platform than they are
125 intended to be run on. Despite they cannot be loaded there (or even
126 when they load they cannot be used due to missing HW support),
127 developers still, opposing to distributors, might want to build such
128 drivers to compile-test them.
130 If you are a developer and want to build everything available, say Y
131 here. If you are a user/distributor, say N here to exclude useless
132 drivers to be distributed.
134 config UAPI_HEADER_TEST
135 bool "Compile test UAPI headers"
136 depends on HEADERS_INSTALL && CC_CAN_LINK
138 Compile test headers exported to user-space to ensure they are
139 self-contained, i.e. compilable as standalone units.
141 If you are a developer or tester and want to ensure the exported
142 headers are self-contained, say Y here. Otherwise, choose N.
145 string "Local version - append to kernel release"
147 Append an extra string to the end of your kernel version.
148 This will show up when you type uname, for example.
149 The string you set here will be appended after the contents of
150 any files with a filename matching localversion* in your
151 object and source tree, in that order. Your total string can
152 be a maximum of 64 characters.
154 config LOCALVERSION_AUTO
155 bool "Automatically append version information to the version string"
157 depends on !COMPILE_TEST
159 This will try to automatically determine if the current tree is a
160 release tree by looking for git tags that belong to the current
161 top of tree revision.
163 A string of the format -gxxxxxxxx will be added to the localversion
164 if a git-based tree is found. The string generated by this will be
165 appended after any matching localversion* files, and after the value
166 set in CONFIG_LOCALVERSION.
168 (The actual string used here is the first eight characters produced
169 by running the command:
171 $ git rev-parse --verify HEAD
173 which is done within the script "scripts/setlocalversion".)
176 string "Build ID Salt"
179 The build ID is used to link binaries and their debug info. Setting
180 this option will use the value in the calculation of the build id.
181 This is mostly useful for distributions which want to ensure the
182 build is unique between builds. It's safe to leave the default.
184 config HAVE_KERNEL_GZIP
187 config HAVE_KERNEL_BZIP2
190 config HAVE_KERNEL_LZMA
193 config HAVE_KERNEL_XZ
196 config HAVE_KERNEL_LZO
199 config HAVE_KERNEL_LZ4
202 config HAVE_KERNEL_ZSTD
205 config HAVE_KERNEL_UNCOMPRESSED
209 prompt "Kernel compression mode"
211 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
213 The linux kernel is a kind of self-extracting executable.
214 Several compression algorithms are available, which differ
215 in efficiency, compression and decompression speed.
216 Compression speed is only relevant when building a kernel.
217 Decompression speed is relevant at each boot.
219 If you have any problems with bzip2 or lzma compressed
220 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
221 version of this functionality (bzip2 only), for 2.4, was
222 supplied by Christian Ludwig)
224 High compression options are mostly useful for users, who
225 are low on disk space (embedded systems), but for whom ram
228 If in doubt, select 'gzip'
232 depends on HAVE_KERNEL_GZIP
234 The old and tried gzip compression. It provides a good balance
235 between compression ratio and decompression speed.
239 depends on HAVE_KERNEL_BZIP2
241 Its compression ratio and speed is intermediate.
242 Decompression speed is slowest among the choices. The kernel
243 size is about 10% smaller with bzip2, in comparison to gzip.
244 Bzip2 uses a large amount of memory. For modern kernels you
245 will need at least 8MB RAM or more for booting.
249 depends on HAVE_KERNEL_LZMA
251 This compression algorithm's ratio is best. Decompression speed
252 is between gzip and bzip2. Compression is slowest.
253 The kernel size is about 33% smaller with LZMA in comparison to gzip.
257 depends on HAVE_KERNEL_XZ
259 XZ uses the LZMA2 algorithm and instruction set specific
260 BCJ filters which can improve compression ratio of executable
261 code. The size of the kernel is about 30% smaller with XZ in
262 comparison to gzip. On architectures for which there is a BCJ
263 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
264 will create a few percent smaller kernel than plain LZMA.
266 The speed is about the same as with LZMA: The decompression
267 speed of XZ is better than that of bzip2 but worse than gzip
268 and LZO. Compression is slow.
272 depends on HAVE_KERNEL_LZO
274 Its compression ratio is the poorest among the choices. The kernel
275 size is about 10% bigger than gzip; however its speed
276 (both compression and decompression) is the fastest.
280 depends on HAVE_KERNEL_LZ4
282 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
283 A preliminary version of LZ4 de/compression tool is available at
284 <https://code.google.com/p/lz4/>.
286 Its compression ratio is worse than LZO. The size of the kernel
287 is about 8% bigger than LZO. But the decompression speed is
292 depends on HAVE_KERNEL_ZSTD
294 ZSTD is a compression algorithm targeting intermediate compression
295 with fast decompression speed. It will compress better than GZIP and
296 decompress around the same speed as LZO, but slower than LZ4. You
297 will need at least 192 KB RAM or more for booting. The zstd command
298 line tool is required for compression.
300 config KERNEL_UNCOMPRESSED
302 depends on HAVE_KERNEL_UNCOMPRESSED
304 Produce uncompressed kernel image. This option is usually not what
305 you want. It is useful for debugging the kernel in slow simulation
306 environments, where decompressing and moving the kernel is awfully
307 slow. This option allows early boot code to skip the decompressor
308 and jump right at uncompressed kernel image.
313 string "Default init path"
316 This option determines the default init for the system if no init=
317 option is passed on the kernel command line. If the requested path is
318 not present, we will still then move on to attempting further
319 locations (e.g. /sbin/init, etc). If this is empty, we will just use
320 the fallback list when init= is not passed.
322 config DEFAULT_HOSTNAME
323 string "Default hostname"
326 This option determines the default system hostname before userspace
327 calls sethostname(2). The kernel traditionally uses "(none)" here,
328 but you may wish to use a different default here to make a minimal
329 system more usable with less configuration.
332 # For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can
333 # add proper SWAP support to them, in which case this can be remove.
339 bool "Support for paging of anonymous memory (swap)"
340 depends on MMU && BLOCK && !ARCH_NO_SWAP
343 This option allows you to choose whether you want to have support
344 for so called swap devices or swap files in your kernel that are
345 used to provide more virtual memory than the actual RAM present
346 in your computer. If unsure say Y.
351 Inter Process Communication is a suite of library functions and
352 system calls which let processes (running programs) synchronize and
353 exchange information. It is generally considered to be a good thing,
354 and some programs won't run unless you say Y here. In particular, if
355 you want to run the DOS emulator dosemu under Linux (read the
356 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
357 you'll need to say Y here.
359 You can find documentation about IPC with "info ipc" and also in
360 section 6.4 of the Linux Programmer's Guide, available from
361 <http://www.tldp.org/guides.html>.
363 config SYSVIPC_SYSCTL
370 bool "POSIX Message Queues"
373 POSIX variant of message queues is a part of IPC. In POSIX message
374 queues every message has a priority which decides about succession
375 of receiving it by a process. If you want to compile and run
376 programs written e.g. for Solaris with use of its POSIX message
377 queues (functions mq_*) say Y here.
379 POSIX message queues are visible as a filesystem called 'mqueue'
380 and can be mounted somewhere if you want to do filesystem
381 operations on message queues.
385 config POSIX_MQUEUE_SYSCTL
387 depends on POSIX_MQUEUE
392 bool "General notification queue"
396 This is a general notification queue for the kernel to pass events to
397 userspace by splicing them into pipes. It can be used in conjunction
398 with watches for key/keyring change notifications and device
401 See Documentation/watch_queue.rst
403 config CROSS_MEMORY_ATTACH
404 bool "Enable process_vm_readv/writev syscalls"
408 Enabling this option adds the system calls process_vm_readv and
409 process_vm_writev which allow a process with the correct privileges
410 to directly read from or write to another process' address space.
411 See the man page for more details.
414 bool "uselib syscall"
415 def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION
417 This option enables the uselib syscall, a system call used in the
418 dynamic linker from libc5 and earlier. glibc does not use this
419 system call. If you intend to run programs built on libc5 or
420 earlier, you may need to enable this syscall. Current systems
421 running glibc can safely disable this.
424 bool "Auditing support"
427 Enable auditing infrastructure that can be used with another
428 kernel subsystem, such as SELinux (which requires this for
429 logging of avc messages output). System call auditing is included
430 on architectures which support it.
432 config HAVE_ARCH_AUDITSYSCALL
437 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
440 source "kernel/irq/Kconfig"
441 source "kernel/time/Kconfig"
442 source "kernel/bpf/Kconfig"
443 source "kernel/Kconfig.preempt"
445 menu "CPU/Task time and stats accounting"
447 config VIRT_CPU_ACCOUNTING
451 prompt "Cputime accounting"
452 default TICK_CPU_ACCOUNTING if !PPC64
453 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
455 # Kind of a stub config for the pure tick based cputime accounting
456 config TICK_CPU_ACCOUNTING
457 bool "Simple tick based cputime accounting"
458 depends on !S390 && !NO_HZ_FULL
460 This is the basic tick based cputime accounting that maintains
461 statistics about user, system and idle time spent on per jiffies
466 config VIRT_CPU_ACCOUNTING_NATIVE
467 bool "Deterministic task and CPU time accounting"
468 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
469 select VIRT_CPU_ACCOUNTING
471 Select this option to enable more accurate task and CPU time
472 accounting. This is done by reading a CPU counter on each
473 kernel entry and exit and on transitions within the kernel
474 between system, softirq and hardirq state, so there is a
475 small performance impact. In the case of s390 or IBM POWER > 5,
476 this also enables accounting of stolen time on logically-partitioned
479 config VIRT_CPU_ACCOUNTING_GEN
480 bool "Full dynticks CPU time accounting"
481 depends on HAVE_CONTEXT_TRACKING
482 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
483 depends on GENERIC_CLOCKEVENTS
484 select VIRT_CPU_ACCOUNTING
485 select CONTEXT_TRACKING
487 Select this option to enable task and CPU time accounting on full
488 dynticks systems. This accounting is implemented by watching every
489 kernel-user boundaries using the context tracking subsystem.
490 The accounting is thus performed at the expense of some significant
493 For now this is only useful if you are working on the full
494 dynticks subsystem development.
500 config IRQ_TIME_ACCOUNTING
501 bool "Fine granularity task level IRQ time accounting"
502 depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE
504 Select this option to enable fine granularity task irq time
505 accounting. This is done by reading a timestamp on each
506 transitions between softirq and hardirq state, so there can be a
507 small performance impact.
509 If in doubt, say N here.
511 config HAVE_SCHED_AVG_IRQ
513 depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING
516 config SCHED_THERMAL_PRESSURE
518 default y if ARM && ARM_CPU_TOPOLOGY
521 depends on CPU_FREQ_THERMAL
523 Select this option to enable thermal pressure accounting in the
524 scheduler. Thermal pressure is the value conveyed to the scheduler
525 that reflects the reduction in CPU compute capacity resulted from
526 thermal throttling. Thermal throttling occurs when the performance of
527 a CPU is capped due to high operating temperatures.
529 If selected, the scheduler will be able to balance tasks accordingly,
530 i.e. put less load on throttled CPUs than on non/less throttled ones.
532 This requires the architecture to implement
533 arch_set_thermal_pressure() and arch_scale_thermal_pressure().
535 config BSD_PROCESS_ACCT
536 bool "BSD Process Accounting"
539 If you say Y here, a user level program will be able to instruct the
540 kernel (via a special system call) to write process accounting
541 information to a file: whenever a process exits, information about
542 that process will be appended to the file by the kernel. The
543 information includes things such as creation time, owning user,
544 command name, memory usage, controlling terminal etc. (the complete
545 list is in the struct acct in <file:include/linux/acct.h>). It is
546 up to the user level program to do useful things with this
547 information. This is generally a good idea, so say Y.
549 config BSD_PROCESS_ACCT_V3
550 bool "BSD Process Accounting version 3 file format"
551 depends on BSD_PROCESS_ACCT
554 If you say Y here, the process accounting information is written
555 in a new file format that also logs the process IDs of each
556 process and its parent. Note that this file format is incompatible
557 with previous v0/v1/v2 file formats, so you will need updated tools
558 for processing it. A preliminary version of these tools is available
559 at <http://www.gnu.org/software/acct/>.
562 bool "Export task/process statistics through netlink"
567 Export selected statistics for tasks/processes through the
568 generic netlink interface. Unlike BSD process accounting, the
569 statistics are available during the lifetime of tasks/processes as
570 responses to commands. Like BSD accounting, they are sent to user
575 config TASK_DELAY_ACCT
576 bool "Enable per-task delay accounting"
580 Collect information on time spent by a task waiting for system
581 resources like cpu, synchronous block I/O completion and swapping
582 in pages. Such statistics can help in setting a task's priorities
583 relative to other tasks for cpu, io, rss limits etc.
588 bool "Enable extended accounting over taskstats"
591 Collect extended task accounting data and send the data
592 to userland for processing over the taskstats interface.
596 config TASK_IO_ACCOUNTING
597 bool "Enable per-task storage I/O accounting"
598 depends on TASK_XACCT
600 Collect information on the number of bytes of storage I/O which this
606 bool "Pressure stall information tracking"
608 Collect metrics that indicate how overcommitted the CPU, memory,
609 and IO capacity are in the system.
611 If you say Y here, the kernel will create /proc/pressure/ with the
612 pressure statistics files cpu, memory, and io. These will indicate
613 the share of walltime in which some or all tasks in the system are
614 delayed due to contention of the respective resource.
616 In kernels with cgroup support, cgroups (cgroup2 only) will
617 have cpu.pressure, memory.pressure, and io.pressure files,
618 which aggregate pressure stalls for the grouped tasks only.
620 For more details see Documentation/accounting/psi.rst.
624 config PSI_DEFAULT_DISABLED
625 bool "Require boot parameter to enable pressure stall information tracking"
629 If set, pressure stall information tracking will be disabled
630 per default but can be enabled through passing psi=1 on the
631 kernel commandline during boot.
633 This feature adds some code to the task wakeup and sleep
634 paths of the scheduler. The overhead is too low to affect
635 common scheduling-intense workloads in practice (such as
636 webservers, memcache), but it does show up in artificial
637 scheduler stress tests, such as hackbench.
639 If you are paranoid and not sure what the kernel will be
644 endmenu # "CPU/Task time and stats accounting"
648 depends on SMP || COMPILE_TEST
651 Make sure that CPUs running critical tasks are not disturbed by
652 any source of "noise" such as unbound workqueues, timers, kthreads...
653 Unbound jobs get offloaded to housekeeping CPUs. This is driven by
654 the "isolcpus=" boot parameter.
658 source "kernel/rcu/Kconfig"
665 tristate "Kernel .config support"
667 This option enables the complete Linux kernel ".config" file
668 contents to be saved in the kernel. It provides documentation
669 of which kernel options are used in a running kernel or in an
670 on-disk kernel. This information can be extracted from the kernel
671 image file with the script scripts/extract-ikconfig and used as
672 input to rebuild the current kernel or to build another kernel.
673 It can also be extracted from a running kernel by reading
674 /proc/config.gz if enabled (below).
677 bool "Enable access to .config through /proc/config.gz"
678 depends on IKCONFIG && PROC_FS
680 This option enables access to the kernel configuration file
681 through /proc/config.gz.
684 tristate "Enable kernel headers through /sys/kernel/kheaders.tar.xz"
687 This option enables access to the in-kernel headers that are generated during
688 the build process. These can be used to build eBPF tracing programs,
689 or similar programs. If you build the headers as a module, a module called
690 kheaders.ko is built which can be loaded on-demand to get access to headers.
693 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
694 range 12 25 if !H8300
699 Select the minimal kernel log buffer size as a power of 2.
700 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
701 parameter, see below. Any higher size also might be forced
702 by "log_buf_len" boot parameter.
712 config LOG_CPU_MAX_BUF_SHIFT
713 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
716 default 12 if !BASE_SMALL
717 default 0 if BASE_SMALL
720 This option allows to increase the default ring buffer size
721 according to the number of CPUs. The value defines the contribution
722 of each CPU as a power of 2. The used space is typically only few
723 lines however it might be much more when problems are reported,
726 The increased size means that a new buffer has to be allocated and
727 the original static one is unused. It makes sense only on systems
728 with more CPUs. Therefore this value is used only when the sum of
729 contributions is greater than the half of the default kernel ring
730 buffer as defined by LOG_BUF_SHIFT. The default values are set
731 so that more than 16 CPUs are needed to trigger the allocation.
733 Also this option is ignored when "log_buf_len" kernel parameter is
734 used as it forces an exact (power of two) size of the ring buffer.
736 The number of possible CPUs is used for this computation ignoring
737 hotplugging making the computation optimal for the worst case
738 scenario while allowing a simple algorithm to be used from bootup.
740 Examples shift values and their meaning:
741 17 => 128 KB for each CPU
742 16 => 64 KB for each CPU
743 15 => 32 KB for each CPU
744 14 => 16 KB for each CPU
745 13 => 8 KB for each CPU
746 12 => 4 KB for each CPU
748 config PRINTK_SAFE_LOG_BUF_SHIFT
749 int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
754 Select the size of an alternate printk per-CPU buffer where messages
755 printed from usafe contexts are temporary stored. One example would
756 be NMI messages, another one - printk recursion. The messages are
757 copied to the main log buffer in a safe context to avoid a deadlock.
758 The value defines the size as a power of 2.
760 Those messages are rare and limited. The largest one is when
761 a backtrace is printed. It usually fits into 4KB. Select
762 8KB if you want to be on the safe side.
765 17 => 128 KB for each CPU
766 16 => 64 KB for each CPU
767 15 => 32 KB for each CPU
768 14 => 16 KB for each CPU
769 13 => 8 KB for each CPU
770 12 => 4 KB for each CPU
773 # Architectures with an unreliable sched_clock() should select this:
775 config HAVE_UNSTABLE_SCHED_CLOCK
778 config GENERIC_SCHED_CLOCK
781 menu "Scheduler features"
784 bool "Enable utilization clamping for RT/FAIR tasks"
785 depends on CPU_FREQ_GOV_SCHEDUTIL
787 This feature enables the scheduler to track the clamped utilization
788 of each CPU based on RUNNABLE tasks scheduled on that CPU.
790 With this option, the user can specify the min and max CPU
791 utilization allowed for RUNNABLE tasks. The max utilization defines
792 the maximum frequency a task should use while the min utilization
793 defines the minimum frequency it should use.
795 Both min and max utilization clamp values are hints to the scheduler,
796 aiming at improving its frequency selection policy, but they do not
797 enforce or grant any specific bandwidth for tasks.
801 config UCLAMP_BUCKETS_COUNT
802 int "Number of supported utilization clamp buckets"
805 depends on UCLAMP_TASK
807 Defines the number of clamp buckets to use. The range of each bucket
808 will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the
809 number of clamp buckets the finer their granularity and the higher
810 the precision of clamping aggregation and tracking at run-time.
812 For example, with the minimum configuration value we will have 5
813 clamp buckets tracking 20% utilization each. A 25% boosted tasks will
814 be refcounted in the [20..39]% bucket and will set the bucket clamp
815 effective value to 25%.
816 If a second 30% boosted task should be co-scheduled on the same CPU,
817 that task will be refcounted in the same bucket of the first task and
818 it will boost the bucket clamp effective value to 30%.
819 The clamp effective value of a bucket is reset to its nominal value
820 (20% in the example above) when there are no more tasks refcounted in
823 An additional boost/capping margin can be added to some tasks. In the
824 example above the 25% task will be boosted to 30% until it exits the
825 CPU. If that should be considered not acceptable on certain systems,
826 it's always possible to reduce the margin by increasing the number of
827 clamp buckets to trade off used memory for run-time tracking
830 If in doubt, use the default value.
835 # For architectures that want to enable the support for NUMA-affine scheduler
838 config ARCH_SUPPORTS_NUMA_BALANCING
842 # For architectures that prefer to flush all TLBs after a number of pages
843 # are unmapped instead of sending one IPI per page to flush. The architecture
844 # must provide guarantees on what happens if a clean TLB cache entry is
845 # written after the unmap. Details are in mm/rmap.c near the check for
846 # should_defer_flush. The architecture should also consider if the full flush
847 # and the refill costs are offset by the savings of sending fewer IPIs.
848 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
852 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT
855 # For architectures that know their GCC __int128 support is sound
857 config ARCH_SUPPORTS_INT128
860 # For architectures that (ab)use NUMA to represent different memory regions
861 # all cpu-local but of different latencies, such as SuperH.
863 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
866 config NUMA_BALANCING
867 bool "Memory placement aware NUMA scheduler"
868 depends on ARCH_SUPPORTS_NUMA_BALANCING
869 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
870 depends on SMP && NUMA && MIGRATION
872 This option adds support for automatic NUMA aware memory/task placement.
873 The mechanism is quite primitive and is based on migrating memory when
874 it has references to the node the task is running on.
876 This system will be inactive on UMA systems.
878 config NUMA_BALANCING_DEFAULT_ENABLED
879 bool "Automatically enable NUMA aware memory/task placement"
881 depends on NUMA_BALANCING
883 If set, automatic NUMA balancing will be enabled if running on a NUMA
887 bool "Control Group support"
890 This option adds support for grouping sets of processes together, for
891 use with process control subsystems such as Cpusets, CFS, memory
892 controls or device isolation.
894 - Documentation/scheduler/sched-design-CFS.rst (CFS)
895 - Documentation/admin-guide/cgroup-v1/ (features for grouping, isolation
896 and resource control)
906 bool "Memory controller"
910 Provides control over the memory footprint of tasks in a cgroup.
914 depends on MEMCG && SWAP
919 depends on MEMCG && !SLOB
927 Generic block IO controller cgroup interface. This is the common
928 cgroup interface which should be used by various IO controlling
931 Currently, CFQ IO scheduler uses it to recognize task groups and
932 control disk bandwidth allocation (proportional time slice allocation)
933 to such task groups. It is also used by bio throttling logic in
934 block layer to implement upper limit in IO rates on a device.
936 This option only enables generic Block IO controller infrastructure.
937 One needs to also enable actual IO controlling logic/policy. For
938 enabling proportional weight division of disk bandwidth in CFQ, set
939 CONFIG_BFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
940 CONFIG_BLK_DEV_THROTTLING=y.
942 See Documentation/admin-guide/cgroup-v1/blkio-controller.rst for more information.
944 config CGROUP_WRITEBACK
946 depends on MEMCG && BLK_CGROUP
949 menuconfig CGROUP_SCHED
950 bool "CPU controller"
953 This feature lets CPU scheduler recognize task groups and control CPU
954 bandwidth allocation to such task groups. It uses cgroups to group
958 config FAIR_GROUP_SCHED
959 bool "Group scheduling for SCHED_OTHER"
960 depends on CGROUP_SCHED
964 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
965 depends on FAIR_GROUP_SCHED
968 This option allows users to define CPU bandwidth rates (limits) for
969 tasks running within the fair group scheduler. Groups with no limit
970 set are considered to be unconstrained and will run with no
972 See Documentation/scheduler/sched-bwc.rst for more information.
974 config RT_GROUP_SCHED
975 bool "Group scheduling for SCHED_RR/FIFO"
976 depends on CGROUP_SCHED
979 This feature lets you explicitly allocate real CPU bandwidth
980 to task groups. If enabled, it will also make it impossible to
981 schedule realtime tasks for non-root users until you allocate
982 realtime bandwidth for them.
983 See Documentation/scheduler/sched-rt-group.rst for more information.
987 config UCLAMP_TASK_GROUP
988 bool "Utilization clamping per group of tasks"
989 depends on CGROUP_SCHED
990 depends on UCLAMP_TASK
993 This feature enables the scheduler to track the clamped utilization
994 of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
996 When this option is enabled, the user can specify a min and max
997 CPU bandwidth which is allowed for each single task in a group.
998 The max bandwidth allows to clamp the maximum frequency a task
999 can use, while the min bandwidth allows to define a minimum
1000 frequency a task will always use.
1002 When task group based utilization clamping is enabled, an eventually
1003 specified task-specific clamp value is constrained by the cgroup
1004 specified clamp value. Both minimum and maximum task clamping cannot
1005 be bigger than the corresponding clamping defined at task group level.
1010 bool "PIDs controller"
1012 Provides enforcement of process number limits in the scope of a
1013 cgroup. Any attempt to fork more processes than is allowed in the
1014 cgroup will fail. PIDs are fundamentally a global resource because it
1015 is fairly trivial to reach PID exhaustion before you reach even a
1016 conservative kmemcg limit. As a result, it is possible to grind a
1017 system to halt without being limited by other cgroup policies. The
1018 PIDs controller is designed to stop this from happening.
1020 It should be noted that organisational operations (such as attaching
1021 to a cgroup hierarchy) will *not* be blocked by the PIDs controller,
1022 since the PIDs limit only affects a process's ability to fork, not to
1026 bool "RDMA controller"
1028 Provides enforcement of RDMA resources defined by IB stack.
1029 It is fairly easy for consumers to exhaust RDMA resources, which
1030 can result into resource unavailability to other consumers.
1031 RDMA controller is designed to stop this from happening.
1032 Attaching processes with active RDMA resources to the cgroup
1033 hierarchy is allowed even if can cross the hierarchy's limit.
1035 config CGROUP_FREEZER
1036 bool "Freezer controller"
1038 Provides a way to freeze and unfreeze all tasks in a
1041 This option affects the ORIGINAL cgroup interface. The cgroup2 memory
1042 controller includes important in-kernel memory consumers per default.
1044 If you're using cgroup2, say N.
1046 config CGROUP_HUGETLB
1047 bool "HugeTLB controller"
1048 depends on HUGETLB_PAGE
1052 Provides a cgroup controller for HugeTLB pages.
1053 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1054 The limit is enforced during page fault. Since HugeTLB doesn't
1055 support page reclaim, enforcing the limit at page fault time implies
1056 that, the application will get SIGBUS signal if it tries to access
1057 HugeTLB pages beyond its limit. This requires the application to know
1058 beforehand how much HugeTLB pages it would require for its use. The
1059 control group is tracked in the third page lru pointer. This means
1060 that we cannot use the controller with huge page less than 3 pages.
1063 bool "Cpuset controller"
1066 This option will let you create and manage CPUSETs which
1067 allow dynamically partitioning a system into sets of CPUs and
1068 Memory Nodes and assigning tasks to run only within those sets.
1069 This is primarily useful on large SMP or NUMA systems.
1073 config PROC_PID_CPUSET
1074 bool "Include legacy /proc/<pid>/cpuset file"
1078 config CGROUP_DEVICE
1079 bool "Device controller"
1081 Provides a cgroup controller implementing whitelists for
1082 devices which a process in the cgroup can mknod or open.
1084 config CGROUP_CPUACCT
1085 bool "Simple CPU accounting controller"
1087 Provides a simple controller for monitoring the
1088 total CPU consumed by the tasks in a cgroup.
1091 bool "Perf controller"
1092 depends on PERF_EVENTS
1094 This option extends the perf per-cpu mode to restrict monitoring
1095 to threads which belong to the cgroup specified and run on the
1096 designated cpu. Or this can be used to have cgroup ID in samples
1097 so that it can monitor performance events among cgroups.
1102 bool "Support for eBPF programs attached to cgroups"
1103 depends on BPF_SYSCALL
1104 select SOCK_CGROUP_DATA
1106 Allow attaching eBPF programs to a cgroup using the bpf(2)
1107 syscall command BPF_PROG_ATTACH.
1109 In which context these programs are accessed depends on the type
1110 of attachment. For instance, programs that are attached using
1111 BPF_CGROUP_INET_INGRESS will be executed on the ingress path of
1115 bool "Misc resource controller"
1118 Provides a controller for miscellaneous resources on a host.
1120 Miscellaneous scalar resources are the resources on the host system
1121 which cannot be abstracted like the other cgroups. This controller
1122 tracks and limits the miscellaneous resources used by a process
1123 attached to a cgroup hierarchy.
1125 For more information, please check misc cgroup section in
1126 /Documentation/admin-guide/cgroup-v2.rst.
1129 bool "Debug controller"
1131 depends on DEBUG_KERNEL
1133 This option enables a simple controller that exports
1134 debugging information about the cgroups framework. This
1135 controller is for control cgroup debugging only. Its
1136 interfaces are not stable.
1140 config SOCK_CGROUP_DATA
1146 menuconfig NAMESPACES
1147 bool "Namespaces support" if EXPERT
1148 depends on MULTIUSER
1151 Provides the way to make tasks work with different objects using
1152 the same id. For example same IPC id may refer to different objects
1153 or same user id or pid may refer to different tasks when used in
1154 different namespaces.
1159 bool "UTS namespace"
1162 In this namespace tasks see different info provided with the
1166 bool "TIME namespace"
1167 depends on GENERIC_VDSO_TIME_NS
1170 In this namespace boottime and monotonic clocks can be set.
1171 The time will keep going with the same pace.
1174 bool "IPC namespace"
1175 depends on (SYSVIPC || POSIX_MQUEUE)
1178 In this namespace tasks work with IPC ids which correspond to
1179 different IPC objects in different namespaces.
1182 bool "User namespace"
1185 This allows containers, i.e. vservers, to use user namespaces
1186 to provide different user info for different servers.
1188 When user namespaces are enabled in the kernel it is
1189 recommended that the MEMCG option also be enabled and that
1190 user-space use the memory control groups to limit the amount
1191 of memory a memory unprivileged users can use.
1196 bool "PID Namespaces"
1199 Support process id namespaces. This allows having multiple
1200 processes with the same pid as long as they are in different
1201 pid namespaces. This is a building block of containers.
1204 bool "Network namespace"
1208 Allow user space to create what appear to be multiple instances
1209 of the network stack.
1213 config CHECKPOINT_RESTORE
1214 bool "Checkpoint/restore support"
1215 select PROC_CHILDREN
1219 Enables additional kernel features in a sake of checkpoint/restore.
1220 In particular it adds auxiliary prctl codes to setup process text,
1221 data and heap segment sizes, and a few additional /proc filesystem
1224 If unsure, say N here.
1226 config SCHED_AUTOGROUP
1227 bool "Automatic process group scheduling"
1230 select FAIR_GROUP_SCHED
1232 This option optimizes the scheduler for common desktop workloads by
1233 automatically creating and populating task groups. This separation
1234 of workloads isolates aggressive CPU burners (like build jobs) from
1235 desktop applications. Task group autogeneration is currently based
1238 config SYSFS_DEPRECATED
1239 bool "Enable deprecated sysfs features to support old userspace tools"
1243 This option adds code that switches the layout of the "block" class
1244 devices, to not show up in /sys/class/block/, but only in
1247 This switch is only active when the sysfs.deprecated=1 boot option is
1248 passed or the SYSFS_DEPRECATED_V2 option is set.
1250 This option allows new kernels to run on old distributions and tools,
1251 which might get confused by /sys/class/block/. Since 2007/2008 all
1252 major distributions and tools handle this just fine.
1254 Recent distributions and userspace tools after 2009/2010 depend on
1255 the existence of /sys/class/block/, and will not work with this
1258 Only if you are using a new kernel on an old distribution, you might
1261 config SYSFS_DEPRECATED_V2
1262 bool "Enable deprecated sysfs features by default"
1265 depends on SYSFS_DEPRECATED
1267 Enable deprecated sysfs by default.
1269 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1272 Only if you are using a new kernel on an old distribution, you might
1273 need to say Y here. Even then, odds are you would not need it
1274 enabled, you can always pass the boot option if absolutely necessary.
1277 bool "Kernel->user space relay support (formerly relayfs)"
1280 This option enables support for relay interface support in
1281 certain file systems (such as debugfs).
1282 It is designed to provide an efficient mechanism for tools and
1283 facilities to relay large amounts of data from kernel space to
1288 config BLK_DEV_INITRD
1289 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1291 The initial RAM filesystem is a ramfs which is loaded by the
1292 boot loader (loadlin or lilo) and that is mounted as root
1293 before the normal boot procedure. It is typically used to
1294 load modules needed to mount the "real" root file system,
1295 etc. See <file:Documentation/admin-guide/initrd.rst> for details.
1297 If RAM disk support (BLK_DEV_RAM) is also included, this
1298 also enables initial RAM disk (initrd) support and adds
1299 15 Kbytes (more on some other architectures) to the kernel size.
1305 source "usr/Kconfig"
1310 bool "Boot config support"
1311 select BLK_DEV_INITRD
1313 Extra boot config allows system admin to pass a config file as
1314 complemental extension of kernel cmdline when booting.
1315 The boot config file must be attached at the end of initramfs
1316 with checksum, size and magic word.
1317 See <file:Documentation/admin-guide/bootconfig.rst> for details.
1322 prompt "Compiler optimization level"
1323 default CC_OPTIMIZE_FOR_PERFORMANCE
1325 config CC_OPTIMIZE_FOR_PERFORMANCE
1326 bool "Optimize for performance (-O2)"
1328 This is the default optimization level for the kernel, building
1329 with the "-O2" compiler flag for best performance and most
1330 helpful compile-time warnings.
1332 config CC_OPTIMIZE_FOR_PERFORMANCE_O3
1333 bool "Optimize more for performance (-O3)"
1336 Choosing this option will pass "-O3" to your compiler to optimize
1337 the kernel yet more for performance.
1339 config CC_OPTIMIZE_FOR_SIZE
1340 bool "Optimize for size (-Os)"
1342 Choosing this option will pass "-Os" to your compiler resulting
1343 in a smaller kernel.
1347 config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1350 This requires that the arch annotates or otherwise protects
1351 its external entry points from being discarded. Linker scripts
1352 must also merge .text.*, .data.*, and .bss.* correctly into
1353 output sections. Care must be taken not to pull in unrelated
1354 sections (e.g., '.text.init'). Typically '.' in section names
1355 is used to distinguish them from label names / C identifiers.
1357 config LD_DEAD_CODE_DATA_ELIMINATION
1358 bool "Dead code and data elimination (EXPERIMENTAL)"
1359 depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
1361 depends on $(cc-option,-ffunction-sections -fdata-sections)
1362 depends on $(ld-option,--gc-sections)
1364 Enable this if you want to do dead code and data elimination with
1365 the linker by compiling with -ffunction-sections -fdata-sections,
1366 and linking with --gc-sections.
1368 This can reduce on disk and in-memory size of the kernel
1369 code and static data, particularly for small configs and
1370 on small systems. This has the possibility of introducing
1371 silently broken kernel if the required annotations are not
1372 present. This option is not well tested yet, so use at your
1375 config LD_ORPHAN_WARN
1377 depends on ARCH_WANT_LD_ORPHAN_WARN
1378 depends on !LD_IS_LLD || LLD_VERSION >= 110000
1379 depends on $(ld-option,--orphan-handling=warn)
1387 config SYSCTL_EXCEPTION_TRACE
1390 Enable support for /proc/sys/debug/exception-trace.
1392 config SYSCTL_ARCH_UNALIGN_NO_WARN
1395 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1396 Allows arch to define/use @no_unaligned_warning to possibly warn
1397 about unaligned access emulation going on under the hood.
1399 config SYSCTL_ARCH_UNALIGN_ALLOW
1402 Enable support for /proc/sys/kernel/unaligned-trap
1403 Allows arches to define/use @unaligned_enabled to runtime toggle
1404 the unaligned access emulation.
1405 see arch/parisc/kernel/unaligned.c for reference
1407 config HAVE_PCSPKR_PLATFORM
1410 # interpreter that classic socket filters depend on
1415 bool "Configure standard kernel features (expert users)"
1416 # Unhide debug options, to make the on-by-default options visible
1419 This option allows certain base kernel options and settings
1420 to be disabled or tweaked. This is for specialized
1421 environments which can tolerate a "non-standard" kernel.
1422 Only use this if you really know what you are doing.
1425 bool "Enable 16-bit UID system calls" if EXPERT
1426 depends on HAVE_UID16 && MULTIUSER
1429 This enables the legacy 16-bit UID syscall wrappers.
1432 bool "Multiple users, groups and capabilities support" if EXPERT
1435 This option enables support for non-root users, groups and
1438 If you say N here, all processes will run with UID 0, GID 0, and all
1439 possible capabilities. Saying N here also compiles out support for
1440 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1443 If unsure, say Y here.
1445 config SGETMASK_SYSCALL
1446 bool "sgetmask/ssetmask syscalls support" if EXPERT
1447 def_bool PARISC || M68K || PPC || MIPS || X86 || SPARC || MICROBLAZE || SUPERH
1449 sys_sgetmask and sys_ssetmask are obsolete system calls
1450 no longer supported in libc but still enabled by default in some
1453 If unsure, leave the default option here.
1455 config SYSFS_SYSCALL
1456 bool "Sysfs syscall support" if EXPERT
1459 sys_sysfs is an obsolete system call no longer supported in libc.
1460 Note that disabling this option is more secure but might break
1461 compatibility with some systems.
1463 If unsure say Y here.
1466 bool "open by fhandle syscalls" if EXPERT
1470 If you say Y here, a user level program will be able to map
1471 file names to handle and then later use the handle for
1472 different file system operations. This is useful in implementing
1473 userspace file servers, which now track files using handles instead
1474 of names. The handle would remain the same even if file names
1475 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
1479 bool "Posix Clocks & timers" if EXPERT
1482 This includes native support for POSIX timers to the kernel.
1483 Some embedded systems have no use for them and therefore they
1484 can be configured out to reduce the size of the kernel image.
1486 When this option is disabled, the following syscalls won't be
1487 available: timer_create, timer_gettime: timer_getoverrun,
1488 timer_settime, timer_delete, clock_adjtime, getitimer,
1489 setitimer, alarm. Furthermore, the clock_settime, clock_gettime,
1490 clock_getres and clock_nanosleep syscalls will be limited to
1491 CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only.
1497 bool "Enable support for printk" if EXPERT
1500 This option enables normal printk support. Removing it
1501 eliminates most of the message strings from the kernel image
1502 and makes the kernel more or less silent. As this makes it
1503 very difficult to diagnose system problems, saying N here is
1504 strongly discouraged.
1512 bool "BUG() support" if EXPERT
1515 Disabling this option eliminates support for BUG and WARN, reducing
1516 the size of your kernel image and potentially quietly ignoring
1517 numerous fatal conditions. You should only consider disabling this
1518 option for embedded systems with no facilities for reporting errors.
1524 bool "Enable ELF core dumps" if EXPERT
1526 Enable support for generating core dumps. Disabling saves about 4k.
1529 config PCSPKR_PLATFORM
1530 bool "Enable PC-Speaker support" if EXPERT
1531 depends on HAVE_PCSPKR_PLATFORM
1535 This option allows to disable the internal PC-Speaker
1536 support, saving some memory.
1540 bool "Enable full-sized data structures for core" if EXPERT
1542 Disabling this option reduces the size of miscellaneous core
1543 kernel data structures. This saves memory on small machines,
1544 but may reduce performance.
1547 bool "Enable futex support" if EXPERT
1551 Disabling this option will cause the kernel to be built without
1552 support for "fast userspace mutexes". The resulting kernel may not
1553 run glibc-based applications correctly.
1557 depends on FUTEX && RT_MUTEXES
1560 config HAVE_FUTEX_CMPXCHG
1564 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1565 is implemented and always working. This removes a couple of runtime
1569 bool "Enable eventpoll support" if EXPERT
1572 Disabling this option will cause the kernel to be built without
1573 support for epoll family of system calls.
1576 bool "Enable signalfd() system call" if EXPERT
1579 Enable the signalfd() system call that allows to receive signals
1580 on a file descriptor.
1585 bool "Enable timerfd() system call" if EXPERT
1588 Enable the timerfd() system call that allows to receive timer
1589 events on a file descriptor.
1594 bool "Enable eventfd() system call" if EXPERT
1597 Enable the eventfd() system call that allows to receive both
1598 kernel notification (ie. KAIO) or userspace notifications.
1603 bool "Use full shmem filesystem" if EXPERT
1607 The shmem is an internal filesystem used to manage shared memory.
1608 It is backed by swap and manages resource limits. It is also exported
1609 to userspace as tmpfs if TMPFS is enabled. Disabling this
1610 option replaces shmem and tmpfs with the much simpler ramfs code,
1611 which may be appropriate on small systems without swap.
1614 bool "Enable AIO support" if EXPERT
1617 This option enables POSIX asynchronous I/O which may by used
1618 by some high performance threaded applications. Disabling
1619 this option saves about 7k.
1622 bool "Enable IO uring support" if EXPERT
1626 This option enables support for the io_uring interface, enabling
1627 applications to submit and complete IO through submission and
1628 completion rings that are shared between the kernel and application.
1630 config ADVISE_SYSCALLS
1631 bool "Enable madvise/fadvise syscalls" if EXPERT
1634 This option enables the madvise and fadvise syscalls, used by
1635 applications to advise the kernel about their future memory or file
1636 usage, improving performance. If building an embedded system where no
1637 applications use these syscalls, you can disable this option to save
1640 config HAVE_ARCH_USERFAULTFD_WP
1643 Arch has userfaultfd write protection support
1646 bool "Enable membarrier() system call" if EXPERT
1649 Enable the membarrier() system call that allows issuing memory
1650 barriers across all running threads, which can be used to distribute
1651 the cost of user-space memory barriers asymmetrically by transforming
1652 pairs of memory barriers into pairs consisting of membarrier() and a
1658 bool "Load all symbols for debugging/ksymoops" if EXPERT
1661 Say Y here to let the kernel print out symbolic crash information and
1662 symbolic stack backtraces. This increases the size of the kernel
1663 somewhat, as all symbols have to be loaded into the kernel image.
1666 bool "Include all symbols in kallsyms"
1667 depends on DEBUG_KERNEL && KALLSYMS
1669 Normally kallsyms only contains the symbols of functions for nicer
1670 OOPS messages and backtraces (i.e., symbols from the text and inittext
1671 sections). This is sufficient for most cases. And only in very rare
1672 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1673 names of variables from the data sections, etc).
1675 This option makes sure that all symbols are loaded into the kernel
1676 image (i.e., symbols from all sections) in cost of increased kernel
1677 size (depending on the kernel configuration, it may be 300KiB or
1678 something like this).
1680 Say N unless you really need all symbols.
1682 config KALLSYMS_ABSOLUTE_PERCPU
1685 default X86_64 && SMP
1687 config KALLSYMS_BASE_RELATIVE
1692 Instead of emitting them as absolute values in the native word size,
1693 emit the symbol references in the kallsyms table as 32-bit entries,
1694 each containing a relative value in the range [base, base + U32_MAX]
1695 or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either
1696 an absolute value in the range [0, S32_MAX] or a relative value in the
1697 range [base, base + S32_MAX], where base is the lowest relative symbol
1698 address encountered in the image.
1700 On 64-bit builds, this reduces the size of the address table by 50%,
1701 but more importantly, it results in entries whose values are build
1702 time constants, and no relocation pass is required at runtime to fix
1703 up the entries based on the runtime load address of the kernel.
1705 # end of the "standard kernel features (expert users)" menu
1707 # syscall, maps, verifier
1710 bool "Enable userfaultfd() system call"
1713 Enable the userfaultfd() system call that allows to intercept and
1714 handle page faults in userland.
1716 config ARCH_HAS_MEMBARRIER_CALLBACKS
1719 config ARCH_HAS_MEMBARRIER_SYNC_CORE
1723 bool "Enable kcmp() system call" if EXPERT
1725 Enable the kernel resource comparison system call. It provides
1726 user-space with the ability to compare two processes to see if they
1727 share a common resource, such as a file descriptor or even virtual
1733 bool "Enable rseq() system call" if EXPERT
1735 depends on HAVE_RSEQ
1738 Enable the restartable sequences system call. It provides a
1739 user-space cache for the current CPU number value, which
1740 speeds up getting the current CPU number from user-space,
1741 as well as an ABI to speed up user-space operations on
1748 bool "Enabled debugging of rseq() system call" if EXPERT
1749 depends on RSEQ && DEBUG_KERNEL
1751 Enable extra debugging checks for the rseq system call.
1756 bool "Embedded system"
1757 option allnoconfig_y
1760 This option should be enabled if compiling the kernel for
1761 an embedded system so certain expert options are available
1764 config HAVE_PERF_EVENTS
1767 See tools/perf/design.txt for details.
1769 config PERF_USE_VMALLOC
1772 See tools/perf/design.txt for details
1775 bool "PC/104 support" if EXPERT
1777 Expose PC/104 form factor device drivers and options available for
1778 selection and configuration. Enable this option if your target
1779 machine has a PC/104 bus.
1781 menu "Kernel Performance Events And Counters"
1784 bool "Kernel performance events and counters"
1785 default y if PROFILING
1786 depends on HAVE_PERF_EVENTS
1790 Enable kernel support for various performance events provided
1791 by software and hardware.
1793 Software events are supported either built-in or via the
1794 use of generic tracepoints.
1796 Most modern CPUs support performance events via performance
1797 counter registers. These registers count the number of certain
1798 types of hw events: such as instructions executed, cachemisses
1799 suffered, or branches mis-predicted - without slowing down the
1800 kernel or applications. These registers can also trigger interrupts
1801 when a threshold number of events have passed - and can thus be
1802 used to profile the code that runs on that CPU.
1804 The Linux Performance Event subsystem provides an abstraction of
1805 these software and hardware event capabilities, available via a
1806 system call and used by the "perf" utility in tools/perf/. It
1807 provides per task and per CPU counters, and it provides event
1808 capabilities on top of those.
1812 config DEBUG_PERF_USE_VMALLOC
1814 bool "Debug: use vmalloc to back perf mmap() buffers"
1815 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1816 select PERF_USE_VMALLOC
1818 Use vmalloc memory to back perf mmap() buffers.
1820 Mostly useful for debugging the vmalloc code on platforms
1821 that don't require it.
1827 config VM_EVENT_COUNTERS
1829 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1831 VM event counters are needed for event counts to be shown.
1832 This option allows the disabling of the VM event counters
1833 on EXPERT systems. /proc/vmstat will only show page counts
1834 if VM event counters are disabled.
1838 bool "Enable SLUB debugging support" if EXPERT
1839 depends on SLUB && SYSFS
1841 SLUB has extensive debug support features. Disabling these can
1842 result in significant savings in code size. This also disables
1843 SLUB sysfs support. /sys/slab will not exist and there will be
1844 no support for cache validation etc.
1847 bool "Disable heap randomization"
1850 Randomizing heap placement makes heap exploits harder, but it
1851 also breaks ancient binaries (including anything libc5 based).
1852 This option changes the bootup default to heap randomization
1853 disabled, and can be overridden at runtime by setting
1854 /proc/sys/kernel/randomize_va_space to 2.
1856 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1859 prompt "Choose SLAB allocator"
1862 This option allows to select a slab allocator.
1866 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1868 The regular slab allocator that is established and known to work
1869 well in all environments. It organizes cache hot objects in
1870 per cpu and per node queues.
1873 bool "SLUB (Unqueued Allocator)"
1874 select HAVE_HARDENED_USERCOPY_ALLOCATOR
1876 SLUB is a slab allocator that minimizes cache line usage
1877 instead of managing queues of cached objects (SLAB approach).
1878 Per cpu caching is realized using slabs of objects instead
1879 of queues of objects. SLUB can use memory efficiently
1880 and has enhanced diagnostics. SLUB is the default choice for
1885 bool "SLOB (Simple Allocator)"
1887 SLOB replaces the stock allocator with a drastically simpler
1888 allocator. SLOB is generally more space efficient but
1889 does not perform as well on large systems.
1893 config SLAB_MERGE_DEFAULT
1894 bool "Allow slab caches to be merged"
1897 For reduced kernel memory fragmentation, slab caches can be
1898 merged when they share the same size and other characteristics.
1899 This carries a risk of kernel heap overflows being able to
1900 overwrite objects from merged caches (and more easily control
1901 cache layout), which makes such heap attacks easier to exploit
1902 by attackers. By keeping caches unmerged, these kinds of exploits
1903 can usually only damage objects in the same cache. To disable
1904 merging at runtime, "slab_nomerge" can be passed on the kernel
1907 config SLAB_FREELIST_RANDOM
1908 bool "Randomize slab freelist"
1909 depends on SLAB || SLUB
1911 Randomizes the freelist order used on creating new pages. This
1912 security feature reduces the predictability of the kernel slab
1913 allocator against heap overflows.
1915 config SLAB_FREELIST_HARDENED
1916 bool "Harden slab freelist metadata"
1917 depends on SLAB || SLUB
1919 Many kernel heap attacks try to target slab cache metadata and
1920 other infrastructure. This options makes minor performance
1921 sacrifices to harden the kernel slab allocator against common
1922 freelist exploit methods. Some slab implementations have more
1923 sanity-checking than others. This option is most effective with
1926 config SHUFFLE_PAGE_ALLOCATOR
1927 bool "Page allocator randomization"
1928 default SLAB_FREELIST_RANDOM && ACPI_NUMA
1930 Randomization of the page allocator improves the average
1931 utilization of a direct-mapped memory-side-cache. See section
1932 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
1933 6.2a specification for an example of how a platform advertises
1934 the presence of a memory-side-cache. There are also incidental
1935 security benefits as it reduces the predictability of page
1936 allocations to compliment SLAB_FREELIST_RANDOM, but the
1937 default granularity of shuffling on the "MAX_ORDER - 1" i.e,
1938 10th order of pages is selected based on cache utilization
1941 While the randomization improves cache utilization it may
1942 negatively impact workloads on platforms without a cache. For
1943 this reason, by default, the randomization is enabled only
1944 after runtime detection of a direct-mapped memory-side-cache.
1945 Otherwise, the randomization may be force enabled with the
1946 'page_alloc.shuffle' kernel command line parameter.
1950 config SLUB_CPU_PARTIAL
1952 depends on SLUB && SMP
1953 bool "SLUB per cpu partial cache"
1955 Per cpu partial caches accelerate objects allocation and freeing
1956 that is local to a processor at the price of more indeterminism
1957 in the latency of the free. On overflow these caches will be cleared
1958 which requires the taking of locks that may cause latency spikes.
1959 Typically one would choose no for a realtime system.
1961 config MMAP_ALLOW_UNINITIALIZED
1962 bool "Allow mmapped anonymous memory to be uninitialized"
1963 depends on EXPERT && !MMU
1966 Normally, and according to the Linux spec, anonymous memory obtained
1967 from mmap() has its contents cleared before it is passed to
1968 userspace. Enabling this config option allows you to request that
1969 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1970 providing a huge performance boost. If this option is not enabled,
1971 then the flag will be ignored.
1973 This is taken advantage of by uClibc's malloc(), and also by
1974 ELF-FDPIC binfmt's brk and stack allocator.
1976 Because of the obvious security issues, this option should only be
1977 enabled on embedded devices where you control what is run in
1978 userspace. Since that isn't generally a problem on no-MMU systems,
1979 it is normally safe to say Y here.
1981 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
1983 config SYSTEM_DATA_VERIFICATION
1985 select SYSTEM_TRUSTED_KEYRING
1989 select ASYMMETRIC_KEY_TYPE
1990 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1993 select X509_CERTIFICATE_PARSER
1994 select PKCS7_MESSAGE_PARSER
1996 Provide PKCS#7 message verification using the contents of the system
1997 trusted keyring to provide public keys. This then can be used for
1998 module verification, kexec image verification and firmware blob
2002 bool "Profiling support"
2004 Say Y here to enable the extended profiling support mechanisms used
2008 # Place an empty function call at each tracepoint site. Can be
2009 # dynamically changed for a probe function.
2014 endmenu # General setup
2016 source "arch/Kconfig"
2023 default 0 if BASE_FULL
2024 default 1 if !BASE_FULL
2026 config MODULE_SIG_FORMAT
2028 select SYSTEM_DATA_VERIFICATION
2031 bool "Enable loadable module support"
2034 Kernel modules are small pieces of compiled code which can
2035 be inserted in the running kernel, rather than being
2036 permanently built into the kernel. You use the "modprobe"
2037 tool to add (and sometimes remove) them. If you say Y here,
2038 many parts of the kernel can be built as modules (by
2039 answering M instead of Y where indicated): this is most
2040 useful for infrequently used options which are not required
2041 for booting. For more information, see the man pages for
2042 modprobe, lsmod, modinfo, insmod and rmmod.
2044 If you say Y here, you will need to run "make
2045 modules_install" to put the modules under /lib/modules/
2046 where modprobe can find them (you may need to be root to do
2053 config MODULE_FORCE_LOAD
2054 bool "Forced module loading"
2057 Allow loading of modules without version information (ie. modprobe
2058 --force). Forced module loading sets the 'F' (forced) taint flag and
2059 is usually a really bad idea.
2061 config MODULE_UNLOAD
2062 bool "Module unloading"
2064 Without this option you will not be able to unload any
2065 modules (note that some modules may not be unloadable
2066 anyway), which makes your kernel smaller, faster
2067 and simpler. If unsure, say Y.
2069 config MODULE_FORCE_UNLOAD
2070 bool "Forced module unloading"
2071 depends on MODULE_UNLOAD
2073 This option allows you to force a module to unload, even if the
2074 kernel believes it is unsafe: the kernel will remove the module
2075 without waiting for anyone to stop using it (using the -f option to
2076 rmmod). This is mainly for kernel developers and desperate users.
2080 bool "Module versioning support"
2082 Usually, you have to use modules compiled with your kernel.
2083 Saying Y here makes it sometimes possible to use modules
2084 compiled for different kernels, by adding enough information
2085 to the modules to (hopefully) spot any changes which would
2086 make them incompatible with the kernel you are running. If
2089 config ASM_MODVERSIONS
2091 default HAVE_ASM_MODVERSIONS && MODVERSIONS
2093 This enables module versioning for exported symbols also from
2094 assembly. This can be enabled only when the target architecture
2097 config MODULE_REL_CRCS
2099 depends on MODVERSIONS
2101 config MODULE_SRCVERSION_ALL
2102 bool "Source checksum for all modules"
2104 Modules which contain a MODULE_VERSION get an extra "srcversion"
2105 field inserted into their modinfo section, which contains a
2106 sum of the source files which made it. This helps maintainers
2107 see exactly which source was used to build a module (since
2108 others sometimes change the module source without updating
2109 the version). With this option, such a "srcversion" field
2110 will be created for all modules. If unsure, say N.
2113 bool "Module signature verification"
2114 select MODULE_SIG_FORMAT
2116 Check modules for valid signatures upon load: the signature
2117 is simply appended to the module. For more information see
2118 <file:Documentation/admin-guide/module-signing.rst>.
2120 Note that this option adds the OpenSSL development packages as a
2121 kernel build dependency so that the signing tool can use its crypto
2124 You should enable this option if you wish to use either
2125 CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via
2126 another LSM - otherwise unsigned modules will be loadable regardless
2127 of the lockdown policy.
2129 !!!WARNING!!! If you enable this option, you MUST make sure that the
2130 module DOES NOT get stripped after being signed. This includes the
2131 debuginfo strip done by some packagers (such as rpmbuild) and
2132 inclusion into an initramfs that wants the module size reduced.
2134 config MODULE_SIG_FORCE
2135 bool "Require modules to be validly signed"
2136 depends on MODULE_SIG
2138 Reject unsigned modules or signed modules for which we don't have a
2139 key. Without this, such modules will simply taint the kernel.
2141 config MODULE_SIG_ALL
2142 bool "Automatically sign all modules"
2144 depends on MODULE_SIG
2146 Sign all modules during make modules_install. Without this option,
2147 modules must be signed manually, using the scripts/sign-file tool.
2149 comment "Do not forget to sign required modules with scripts/sign-file"
2150 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
2153 prompt "Which hash algorithm should modules be signed with?"
2154 depends on MODULE_SIG
2156 This determines which sort of hashing algorithm will be used during
2157 signature generation. This algorithm _must_ be built into the kernel
2158 directly so that signature verification can take place. It is not
2159 possible to load a signed module containing the algorithm to check
2160 the signature on that module.
2162 config MODULE_SIG_SHA1
2163 bool "Sign modules with SHA-1"
2166 config MODULE_SIG_SHA224
2167 bool "Sign modules with SHA-224"
2168 select CRYPTO_SHA256
2170 config MODULE_SIG_SHA256
2171 bool "Sign modules with SHA-256"
2172 select CRYPTO_SHA256
2174 config MODULE_SIG_SHA384
2175 bool "Sign modules with SHA-384"
2176 select CRYPTO_SHA512
2178 config MODULE_SIG_SHA512
2179 bool "Sign modules with SHA-512"
2180 select CRYPTO_SHA512
2184 config MODULE_SIG_HASH
2186 depends on MODULE_SIG
2187 default "sha1" if MODULE_SIG_SHA1
2188 default "sha224" if MODULE_SIG_SHA224
2189 default "sha256" if MODULE_SIG_SHA256
2190 default "sha384" if MODULE_SIG_SHA384
2191 default "sha512" if MODULE_SIG_SHA512
2193 config MODULE_COMPRESS
2194 bool "Compress modules on installation"
2197 Compresses kernel modules when 'make modules_install' is run; gzip or
2198 xz depending on "Compression algorithm" below.
2200 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2202 Out-of-tree kernel modules installed using Kbuild will also be
2203 compressed upon installation.
2205 Note: for modules inside an initrd or initramfs, it's more efficient
2206 to compress the whole initrd or initramfs instead.
2208 Note: This is fully compatible with signed modules.
2213 prompt "Compression algorithm"
2214 depends on MODULE_COMPRESS
2215 default MODULE_COMPRESS_GZIP
2217 This determines which sort of compression will be used during
2218 'make modules_install'.
2220 GZIP (default) and XZ are supported.
2222 config MODULE_COMPRESS_GZIP
2225 config MODULE_COMPRESS_XZ
2230 config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
2231 bool "Allow loading of modules with missing namespace imports"
2233 Symbols exported with EXPORT_SYMBOL_NS*() are considered exported in
2234 a namespace. A module that makes use of a symbol exported with such a
2235 namespace is required to import the namespace via MODULE_IMPORT_NS().
2236 There is no technical reason to enforce correct namespace imports,
2237 but it creates consistency between symbols defining namespaces and
2238 users importing namespaces they make use of. This option relaxes this
2239 requirement and lifts the enforcement when loading a module.
2243 config TRIM_UNUSED_KSYMS
2244 bool "Trim unused exported kernel symbols" if EXPERT
2245 depends on !COMPILE_TEST
2247 The kernel and some modules make many symbols available for
2248 other modules to use via EXPORT_SYMBOL() and variants. Depending
2249 on the set of modules being selected in your kernel configuration,
2250 many of those exported symbols might never be used.
2252 This option allows for unused exported symbols to be dropped from
2253 the build. In turn, this provides the compiler more opportunities
2254 (especially when using LTO) for optimizing the code and reducing
2255 binary size. This might have some security advantages as well.
2257 If unsure, or if you need to build out-of-tree modules, say N.
2259 config UNUSED_KSYMS_WHITELIST
2260 string "Whitelist of symbols to keep in ksymtab"
2261 depends on TRIM_UNUSED_KSYMS
2263 By default, all unused exported symbols will be un-exported from the
2264 build when TRIM_UNUSED_KSYMS is selected.
2266 UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept
2267 exported at all times, even in absence of in-tree users. The value to
2268 set here is the path to a text file containing the list of symbols,
2269 one per line. The path can be absolute, or relative to the kernel
2274 config MODULES_TREE_LOOKUP
2276 depends on PERF_EVENTS || TRACING || CFI_CLANG
2278 config INIT_ALL_POSSIBLE
2281 Back when each arch used to define their own cpu_online_mask and
2282 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2283 with all 1s, and others with all 0s. When they were centralised,
2284 it was better to provide this option than to break all the archs
2285 and have several arch maintainers pursuing me down dark alleys.
2287 source "block/Kconfig"
2289 config PREEMPT_NOTIFIERS
2299 Build a simple ASN.1 grammar compiler that produces a bytecode output
2300 that can be interpreted by the ASN.1 stream decoder and used to
2301 inform it as to what tags are to be expected in a stream and what
2302 functions to call on what tags.
2304 source "kernel/Kconfig.locks"
2306 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
2309 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
2312 # It may be useful for an architecture to override the definitions of the
2313 # SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
2314 # and the COMPAT_ variants in <linux/compat.h>, in particular to use a
2315 # different calling convention for syscalls. They can also override the
2316 # macros for not-implemented syscalls in kernel/sys_ni.c and
2317 # kernel/time/posix-stubs.c. All these overrides need to be available in
2318 # <asm/syscall_wrapper.h>.
2319 config ARCH_HAS_SYSCALL_WRAPPER
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